[Epic] [Feedback SDKs] Support captureFeedback API in all platforms (new envelope format)

[aliu39]

Feedback integrations should start sending the new envelope format instead of the old one.

Use this as a central index to track tickets/PRs for this goal, across repos.

• Javascript: feat(feedback): Add captureFeedback method sentry-javascript#11428
• Dotnet: Support for Feedback Events sentry-dotnet#3605
• React native: Add new captureFeedback API to RN SDK sentry-react-native#3859
• Java/Android: [Android] New User Feedback sentry-java#3599
• Cocoa/iOS: Support for captureFeedback function sentry-cocoa#4187
• Flutter: Support captureFeedback sentry-dart#2230

Docs tasks:

• Update https://develop.sentry.dev/sdk/expected-features/#user-feedback (still references old feedback)
• Document protocol of new feedback: https://develop.sentry.dev/sdk/data-model/envelope-items/#user-feedback #64700
• SDK dev docs for User Feedback v2 sentry-docs#11635
• [User Feedback] Improve JS example by splitting 'crash report' and 'stand-alone user feedback' use cases sentry-docs#10822
• (Ongoing) Maintain supported list at https://docs.sentry.io/product/user-feedback/setup/

Follow-ups for supported platforms:

• Update onboarding
  • JS
  • React native
  • Flutter